Vehicle tracking system using smart-phone as active transponder

ABSTRACT

A system for tracking vehicle position using a smart phone in the vehicle as an active transponder, which is detected by roadside equipment is disclosed. In an embodiment, the system uses existing RF transceivers on the smart-phone, such as Bluetooth LE or WiFi to periodically transmit an identifying message. Road-based equipment detects and locates the smart phone. In a further embodiment, the smart phone is alerted by roadside beacons and only then responds with its identification information. Processing can be performed either on the smart phone or by roadside or central office equipment as is the case in prior art active or passive transponder-based tolling systems. Vehicle location detection can be enhanced through the use of directional antenna matrices such as a Butler matrix. The system can be used for automated roadway tolling and monitoring.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/058,951, filed Mar. 2, 2016, which claims priority under 35 U.S.C.119(e) from U.S. Provisional Patent Application No. 62/266,422 filedDec. 11, 2015; U.S. Provisional Patent Application No. 62/214,638 filedSep. 4, 2015; U.S. Provisional Patent Application No. 62/184,162 filedJun. 24, 2015; U.S. Provisional Patent Application No. 62/156,090 filedMay 1, 2015; U.S. Provisional Patent Application No. 62/127,649 filedMar. 3, 2015; and all bearing the same title as the present application.The entire disclosures of the applications listed above, including anydrawings and appendices are hereby incorporated herein by reference intheir entireties.

FIELD OF THE INVENTION

The invention relates generally to the field of vehicle tracking andtolling.

BACKGROUND

The field of electronic vehicle tracking for tolling and other purposeshas seen many iterations over the years. These include the use ofvehicle-based backscatter transponders detected and communicated with byroadside equipment, active transponders detected and communicated withby roadside equipment, hybrid transponders having both active andbackscatter functions; video monitoring of vehicle license plate andother placards. Cellular telephones have also been described for use intolling systems, alone or in combination with the aforementioned typesof transponders, including in application Ser. No. 13/398,337 by one ormore of the present inventors.

One problem in tolling applications that exists regardless of thetechnology used is determination of the roadway lane in which thevehicle is travelling. This is critical for several reasons. Firstly,because open road tolling systems frequently employ multiple transponderdetection antennas and systems to cover multiple lanes of travel, it isnecessary to accurately determine lane of travel so that vehicles arenot recorded more than once per crossing. Secondly, various tolling androadway traffic management operations provide incentives and/orrestrictions for vehicles of different types and occupancy levels, theseinclude the ability to travel in restricted lanes, thus it is necessaryto determine if a vehicle is travelling in the required or allowed lane.

The present invention is directed to novel approaches to vehicletracking and tolling using smart phones as active transponders. A smartphone is defined here as a cellular phone that also has capability toload and run application programs (apps) and that has wirelesstransceivers beyond the radio used to send voice and data to a cellularnetwork.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an exemplary embodiment of the inventive system.

FIG. 2 is a diagram of an exemplary embodiment of the inventive system.

FIG. 3 is a diagram of an exemplary embodiment of the inventive system.

FIG. 4 is a diagram of an exemplary embodiment of the smart phone of theinventive system.

FIG. 5 is a diagram of an exemplary Prior Art 8×8 Butler Matrix antennaarray.

FIG. 6 is test results of a test-setup using two Butler Matrix antennaarrays.

FIG. 7 is a diagram of an exemplary three-lane system bounded by aGeo-fence.

FIG. 8 is a graph of RSSI versus time for beacons in two locations.

DETAILED DESCRIPTION

Most generally, the system consists of vehicle-based smart phonesinteracting with external fixed transceivers mounted over the roadway orbeside it. The phones and external transceivers are capable of two-waycommunications, and both transmit and receive functions can be utilizedin the system.

The system concept of operations may take several forms:

-   -   The phone may transmit to the fixed transceiver    -   The phone may receive from the fixed transceiver    -   There may be two-way communication between the fixed transceiver        and phone    -   The wireless protocol may be Bluetooth® Low Energy (BLE), IEEE        802.11/WiFi, or an emergent protocol    -   A fixed transceiver may utilize a multi-beam antenna    -   A fixed transceiver may utilize one or more antennas, each        providing a single beam covering a single lane or geographic        area    -   Determination of the vehicle's lane of travel or area may be        computed by:    -   A controller in communication with the fixed transceivers, or    -   The mobile unit. In this case, the mobile can transmit its lane        number or area to a back office via cellular network, WiFi, BLE,        RFID, or any other wireless protocol in use in the phone.

Communication Protocols

Standard radio protocols such as WiFi and BLE may be used for thetransaction, and in principal any protocol with relevant hardware in thephone may be used subject to practical restrictions inherent in theprotocol, hardware, and phone software. WiFi probe requests and BLEadvertisements are examples of signal formats that can function asbeacons in this system. The system can rely on this message alone forlane determination, or additionally utilize responses to the beacon.

To communicate with the smart phone app, fixed transceivers that utilizeWiFi and/or BLE protocols are installed in the lane and connected toappropriate antennas. Messages from the phone contain a uniqueidentifier or ID; these messages can be evaluated for received signalstrength indication (RSSI). Lane position or proximate antenna positioncan be determined at a roadside server connected to the transceivers byEthernet and TCP/IP or other convenient protocol. When a phone messageis received at more than one transceiver across the roadway, the uniqueidentifier, along with the RSSI, are sent to the server.

Alternately, the lane determination may be made by the phone applicationresident and running on the phone, based on messages sent from the fixedtransceivers to the phone.

Phone as Transmitter

In an embodiment, the invention involves configuring a smart phone as anactive transponder for vehicle tracking and/or roadway tolling. Thesmart phone is adapted to transmit a message periodically that containsa known address or identifier. An exemplary system is described withreference to FIGS. 1-4, with like numbers representing the indicatedelements. An existing radio supported on the smart phone 1 such as theWiFi radio or the BLE radio is used to generate these signals. Roadsideand/or overhead transceivers detect the transmissions to identify thelocation of the vehicle. The phone must be uniquely associated with datacontent in the message which is associated with an account used tocollect the payment of tolls.

In order to perform this task effectively it is necessary that the phonesend messages frequently while within the toll zone. A minimumrepetition rate of 10 Hz, or one per 100 milliseconds, is required, but100 Hz or one per 10 milliseconds is preferred. Depending upon powerconsumption in this high rep rate mode, it may be necessary to overlayGeoZone functionality, such that the higher rep rate/power consumptionmode operates only in the vicinity of toll collection zones, thuscreating a low duty cycle operation to preserve cell phone batterycapacity. GeoZone functionality can be implemented by comparing currentGPS position (established by phone's internal GPS receiver/processor 14)to stored geo-location zones selected to include toll point locations. Alimitation on this approach is the maximum number of GeoZones in aniPhone is 20. Alternate methods include using BLE beacons 9 to indicateto the phone application 17 that it is in the vicinity of a tollcollection point, or by using WiFi AP's 8 SSID's or MAC addresses thatare detected by the phone using the phone's WiFi 15 radio.

Signal Strength of Smart Phone Signal for Lane Determination

The basic concept of identifying the travel lane relies on RSSI,provided by common WiFi and BLE transceivers used in mobile phones andfixed transceivers. RSSI-based algorithms for range and directiondetermination must be used with care owing to:

-   -   Multipath corruption, occurring when the radio wave from a        transmitter bounces off obstacles in its path and arrives at the        target with relatively small time offsets from the direct path,    -   Antenna patterns with nulls in particular directions, and    -   Sensitivity to polarization.

In any system architecture, it is clear that there are several feasiblemethods of data processing to determine the lane of travel. Theimplemented solution also depends on antenna type and location, and alsoon the disposition of the phone as a transmitter or receiver. In oneapproach with a phone transmitting and one antenna per lane, theroadside server 20 looks only at messages that meet a minimum thresholdof signal strength received from the smart phone, then compares thesignal strengths received from each antenna to determine the strongestone over a specified period on the order of 30 ms. As the smart phonetraverses the roadway each period has a count assigned based on thestrongest signal strength received on an antenna. The most proximateantenna or alternatively the lane of travel is determined to be theantenna or lane with the most counts in a larger second period (roughly300 ms) or the total such counts during a the entire period required totraverse the section of roadway.

FIG. 3 shows an exemplary design using multi-beam antennas 3 fed byButler matrices, creating highly directional beam patterns 30, 30′, 31,31′, 32 and 32′. By determining the strongest signal path between eachantenna and the phone, either received from the smart phone, it ispossible to very accurately determine position of the phone andpresumable the vehicle. In the example shown, the smart phone ispositioned for best reception in beams 31 and 30′, and it is a simplematter from there to determine that these beams intersect in Lane 1.

Phone as Receiver

In one variation of the system multiple BLE transmitters, or “beacons”9, can be installed across the roadway on a gantry 5 and connected tohigh gain antennas 6. A high gain antenna for purposes of thisspecification is an antenna with a gain of 8 db or higher.

In an embodiment, the beacon ID and time stamp are included in itstransmitted data to allow the mobile to identify its location at a timestamp. The beacon transmits at a high rate, approximately once per 20milliseconds. The beacon time stamp is synchronized to local system timeto resolve transactions. Specialized beacons with high gain can be usedfor tracking or localization.

An exemplary beacon is the iBeacon, which uses a protocol developed byApple®. Various vendors have since made iBeacon-compatible hardwaretransmitters that advertise their ID to nearby portable electronicdevices. The technology enables smart phones, tablets and other devicesto perform actions when in close proximity to an iBeacon.

In an embodiment, the phone receives messages from multiple Beacons andstores relevant data fields such as beacon ID, plaza and lane number,latitude/longitude, time and date, and RSSI.

As battery life on mobile devices is a key product differentiator, somedevices limit the transmit rate or the effective receive rate forwireless transceivers. For example, iPhones apply such limits to the BLEfunctionality, resulting in

-   -   A maximum transmission rate that is less than the BLE standard        maximum.    -   A diminished sample rate when the device is scanning for        beacons; that is, the sample rate is less than the BLE        transmission standard maximum, so samples cannot keep up with        beacons transmitting at that rate.        These restrictions are relaxed, however, when the iPhone is        detecting an iBeacon, so while it is in range of an iBeacon it        is able to record BLE beacon data in background/sleep mode at        nearly the same rate as the beacon advertising rate. This        requires a system architecture that contains iBeacons to        “awaken” iPhones® and beacons to provide advertisements for the        toll transaction. The iBeacons must have a coverage zone that        extends well upstream from the toll plaza to provide sufficient        time for the phones to be ready to record beacon data when        travelling through the plaza. A single antenna or multiple low        gain antennas may be used to provide a wide area communications        zone to accomplish successful reception of the iBeacon message.        These are used in combination with high gain antennas used for        the subsequent beacon messages which form a more constrained        communication zone. The phone can transmit log data to a server        for post processing and analysis, or preferentially analyze it        to determine lane number and transmit that information to a        server.

The simplest approach, when the phone is acting as a receiver and beacontransmitters are fixed across a roadway, is to transmit BLE undirectednon-connectable advertisements. The format of the advertisement messageis defined in the BLE standard, and includes 31 bytes of user-defineddata that can include all relevant information for a toll transaction.The phones operate as BLE passive scanners and do not transmit. Anindividual phone would likely hear multiple beacons as it traverses atoll plaza, and would have to process the data to determine lanelocation or transfer the data to a back office for post-processing,including lane location.

Non-connectable, undirected BLE advertisements have a minimum timeinterval between advertisements of 100 msec. This time represents 14.7feet for a vehicle traveling at 100 mph. Shorter time intervals arenecessary for accurate signal strength histories, and are also usefulfor timing coordination with existing sub-systems in a toll plaza suchas video camera systems. Connectable, directed BLE advertisements have aminimum time interval between advertisements of 20 msec, or 2.9 feet fora vehicle traveling at 100 mph. This provides much improved resolutionwhile eliciting BLE scan requests from mobiles.

Further time resolution may be achieved by including multiple BLEmodules in a beacon. For instance, two beacons can share an RFconnection to an antenna, making the effective advertisement intervalequal to 10 msec. The mobile application would have to correctlyinterpret advertisements from both beacons as coming from the same lane,a simple matter of software. Finally, a high duty cycle mode exists inBLE connectable directed advertisements, where the maximum advertisinginterval is 3.75 msec. This would provide a significant increase inresolution, perhaps more than necessary for a toll system. However, notall devices support this high duty cycle mode.

The data recorded on the phone would likely include, at a minimum, timestamp, beacon ID, and RSSI for each sample. The sample plot in FIG. 8displays BLE RSSI recorded on a phone located in a vehicle travelingthrough a lane with a Beacon overhead in the travel lane and anotherBeacon overhead in an adjacent lane. The difference in peak signalstrength between two Beacons is clear, and one Beacon is clearlystronger for the majority of the record.

This concept is not restricted to BLE, as the wireless protocol could beWiFi or any other that is available on a smart phone.

Signal Strength of Beacon Signal for Lane Determination

In an approach, multiple messages may be transmitted by a BLEtransceiver, or “beacon”, through a high gain antenna and received bythe smart phone. The high gain antenna will be generally set up on anoverhead gantry with maximum gain direction pointing towards the roadsurface or slightly up-tilted toward vehicles as they approach the tollpoint, forming a capture zone on the road where vehicles are in positionto communicate with the beacons. While the capture zones for each beaconwill overlap in a typical case of one antenna per standard-width lane,higher signal strengths tend to occur near the antenna boresight.Because the lane numbers are associated with beacons with known IDs, thelocation of the vehicle can be determined by analyzing RSSI data for thebeacons captured on the phone. The phone application 17 may evaluate thenumber of messages received and the RSSI values from each beacon todetermine the position of the phone relative to the beacons, hence thelane. The toll can then be collected from an account associated with theunique ID for the vehicle passing the toll point in that particularlane, wherein the lane/proximate antenna/beacon information is sent withthe unique ID to the toll system and or account service center. Oneapproach in this case is that the application on the phone compares thesignal strengths received from each beacon antenna to determine thestrongest one over a specified period, say 30 milliseconds. As the phonetraverses the roadway, each period has a count assigned based on thestrongest signal strength received on an antenna, the most proximateantenna or alternatively the lane of travel is determined to be theantenna or lane with the most counts in a larger second period (say 300milliseconds) or the total such counts during a the entire periodrequired to traverse the section of roadway.

Another simple algorithm to make the lane determination is to examinethe strongest N samples for all beacons and average them to create asingle number for each lane. This may be thought of as a low-orderestimate of the area under the curves, proportional to energy, andpossessing increasing accuracy as N increases. As N increases, morecalculations are required which increase the burden on the processor.Hence a proper value for N is a tradeoff between accuracy and processorburden. In practice, the number N can be arrived at through trial anderror. In the case summarized in FIG. 8, the difference in the averagesbetween the correct lane and adjacent lane is 13 dB, using N=10. Thedifference of 13 dB is also approximately equal to the peaks of thecurves. Utilizing a single peak value would provide the correct answerin many cases, but RF multipath can corrupt a single sample more easilythan several samples.

To assign the best time stamp for correlating the vehicle passage toother lane sensors, a straightforward algorithm is to use the median ofthe time stamps for the five data points with highest RSSI in theassigned lane as can be performed for example on the plot in FIG. 8.This synchronized and accurate time stamp combined with accurate laneposition allows the transaction to be accurately post-processed into thetoll system transaction.

To use the system, users download an application with the foregoingcapabilities to the smart phone. Upon download of the phone application,the user will use application-supported account management features toset up an account with the appropriate toll authority or third partyservice provider, create a link between the unique ID/addressinformation to the account, and provide a means for the settlement oftoll charges associated with the unique ID (such as a credit card).

Zone Definition With Geo-fencing and iBeacons®

The overall goal is to be able to determine which lane a vehicle andphone are in based on messages received from multiple BLE beacons. In anembodiment, upon receiving beacon messages and leaving a Geo-fence areaor iBeacon® zone, the raw beacon log data is transferred from smartphone to server for transaction analysis/processing. See FIG. 8 fordiagram of beacons within a Geo-fence.

Smart Phone Stores Beacon Time Information and Reports Later

Alternatively, the smart phone application can simply save theBluetooth® LE beacon messages as the smart phone passes under the highgain beacons on the toll facility. The messages will contain, at aminimum, data identifying the location of the toll lane and the time thebeacon message was sent. The smart phone will normally receive multiplemessages from multiple beacons while traversing the toll plaza. A clockin the beacon establishes the time in the message and is synchronized tothe other toll equipment to a sufficient resolution (say 1-100 ms) toallow the transaction to be correlated based on the time of thetransaction with other elements of the toll system such as a vehicledetection system or a video-based license plate reading system. Thissaved data is then sent as soon as practical via any of the smartphone's data connections (Bluetooth®, WiFi, WAN data) to a server wherethe processing to determine the lane position described above isexecuted. In this case the server need not be located roadside but canbe located anywhere.

In one embodiment a Geo-fence function is used to determine when thebuffered BLE beacon messages or processed results should be sent to theserver over an available data connection. Geo-fence applications arewell known in the art and provide a function to allow a specific area tobe defined such that an alert is generated when the Geo-zone area isentered or exited. A Geo-zone can be created around the toll plaza orarea. When the area is exited an alert triggers the sending of theprocessed or unprocessed beacon data to the server for post processinginto the toll transaction. Similarly a Geo-zone can be establisheddownstream of the toll point where traffic must traverse, and entry intothis Geo-zone can also trigger the sending of buffered data to theserver for processing.

It may not be possible given the state of smart phone technology orlimitations in smart phone systems to send beacon data in real time tothe server. However, because the beacon data contains a time stampsynchronized to the toll system at the toll plaza, a toll transactioncan be generated and post-processed with other data collected from othertoll sensors proximate to the roadway to form a complete tolltransaction. For example, most toll systems include a video-basedenforcement/toll system at the toll plaza. Such systems use varioustechniques well known in the art to take a photo of the vehicle licenseplate which can later be processed and “read” automatically by acomputer. In prior art systems, the toll payment is made by an RFIDreader reading an RFID tag associated with a user account that settledto the users credit card or bank account. If this toll payment is made,the photo taken of the license plate is associated with the vehicle neednot be processed and can be discarded or stored according to policy. Ifa payment is not made, either a violation against the vehicle owner ofrecord or a video-based toll against an account or the vehicle owner ofrecord is processed.

One advantage of post processing the transaction data is thatsubstantially all of the data points collected on the transactionbetween the beacon and the smart phone can be collected and used todetermine the lane position and to determine a time stamp for thetransaction that best represents when the vehicle passed under theantenna. More data typically means better quality output result foralmost any reasonable algorithm used to determine vehicle positionrelative to the beacon antennas.

Typically a trigger system is used, employing one of many vehicledetection technologies known in the art, to determine the vehicle'slocation on the roadway to take the photo of the license plate. In orderto allow toll payment by smart phone rather than RFID tag, the phoneapplication requires the user to establish an account with the tollauthority, or through a private third party account consolidator whosets up a consolidated account for the user with multiple toll agencies.At that time an account identifier is established by the application orby an account server in communication with the application over aninternet connection supported by the smart phone. That accountidentifier is sent by the smart phone when the processed or unprocessedbeacon data is sent to the server, typically after a Geo-fence oriBeacon zone exit event occurs to trigger the sending of this data. Thetrigger point for the license plate photograph is aligned to thedirection of maximum gain of the antenna, allowing the determined travellane to be associated with an accurate time stamp. As this time stamp isalso synchronized with the video system, the beacon transaction can becompared to the video transaction to ensure they are from the samevehicle, eliminating the need for the license plate photo to beprocessed.

Typically, this transaction from the smart phone will not occur in realtime. This is because the sending of the data will be triggered by anevent such as a GeoZone exit (or entry) event, iBeacon read zone exit,or RSSI residing below a threshold for an elapsed time, all of whichoccur after the vehicle has passed through the toll plaza. Additionalsources of latency in the communications network will add to this. Allof the data collected as the vehicle traverses the plaza is availablefor the algorithm that determines lane and time of passage. It alsoimplies that the photo data and any other associated sensor datapertaining to the toll transaction must be stored for some period oftime to allow receipt and processing of the data from the smart phone tocreate the toll transaction, so that it may be post processed againstthis stored data as described above. The minimum period of storage, andthe resulting storage capacity are determined based on the maximumexpected delay in sending and processing the smart phone data so that itmay be post processed. Alternatively, all such data may be permanentlystored according to policy.

In Apple's® iOS operating system applications that are not activelybeing used by the user operate in the background. Usually theseapplications cannot process data or access resources to preserve batterylife. In the contemplated system it is highly advantageous to avoid theneed for user action, as a matter of customer convenience and drivingsafety. There are some exceptions in iOS that will allow some processingtime to be allocated to an application running in the background. Oneexception involves the use of geographical areas. Upon entering ageographical area, the phone application can be automatically launchedor elevated in priority by the operating system. Upon receipt of BLEdata expected by or intended for the phone application, iOS will providea specific allotment of time for the application to process the BLEdata. In one embodiment all of the stored BLE messages received areuploaded to the server over the WAN data link using a web services call.

Another approach to resource conservation while the toll applicationsits in the background is to create iBeacon zones in the roadways thathave beacon zones within them. The iPhone will not log iBeaconadvertisements at a rate faster than one per second, regardless of theiBeacon advertisement rate. It will record beacon advertisements muchfaster in general, and approximately at the same rate as theadvertisement itself, if the iPhone® is in range of an iBeacon.

Data Transfer

In a further embodiment, transaction data is stored in a file on thephone. Data can be received and logged even with the phone in sleepmode. Data is downloaded to a server with no user intervention,triggered by an event such as a Geo-fence trigger described above.Because data will not be downloaded in real time, transactions must bepost-processed into the toll transaction to be correlated with datataken at the toll area, such as video or camera recording of licenseplate, and vehicle detection.

Approach Using Conventional Transponder as Repeater

In one alternative, a transponder device is installed in theconventional electronic toll lane in a similar fashion to how testtransponders are used today. The transponder acts as a repeater of theinformation transmitted by the smart phone. The transponder contains aBLE or WiFi transceiver which receives transaction information from thephone to include the phone unique ID. When interrogated by a reader, thetransponder will mimic the type of message sent in conventionalelectronic toll messages with an account ID associated with the phoneunique ID. In this way the system described above can be implementedwith minimal or no changes in the software and integration of the tollsystem or conventional back office/service center.

Streamlined Transaction

In another embodiment, BLE beacons broadcast advertisements via antennas6 that are typically dispersed one per lane, although two per lane maybe used, or fewer than one per lane may be used. When received in anapplication resident on the smart phone 17 these advertisements triggerresponse messages sent by either the BLE radio 9 or WiFi 8 radio in thesmart phone with a data response similar to how prior art active RFIDtransponders behave today. Simultaneously, these BLE Beacon messagescould trigger return messages to the toll system over any combination ofWiFi, BLE or common carrier WAN data connection present on almost allsmart phones. These responses contain information that is sent to aservice center for the settling of toll collection related to thevehicles' use of the roadway. This information is transmitted to theservice center either by a toll system network of the type commonly usedtoday (in the case of WiFi or BLE return message) or via the WANconnection 10 directly from the smart phone to the service center, orany combination thereof which provides for redundancy of messaging andtherefore enhanced reliability. In all cases the return message withunique identifier is received at the service center where accountsettlement is performed, and the toll is settled to the accountassociated with it. In a further embodiment, a smart phone is a receiverinitially scanning passively for BLE advertisements from the beacons asit enters a capture zone. Upon decoding an advertisement, the phoneoptionally sends a BLE Scan Request (SCAN_REQ PDU) to the beacon. Therequest payload consists of the beacon address and the phone MACaddress. The beacon issues a BLE Scan Response (SCAN_RSP PDU) inresponse to each received SCAN_REQ. The total number of scan responsesrepresents the number of transactions with a phone.

The timestamp for the transaction resides in the scan request payloadand must match the timestamp for other toll systems (i.e. videocameras), within an allowable tolerance.

At the completion of the transaction, the system composes an encrypteddata packet containing the phone MAC address, time and date, plaza andlane ID. This is sent to a back office via typical means, for exampleeither over land line communications such as an internet connection orwirelessly such as by a cellular data connection, and checked againstvideo data for violations.

RF Considerations

In an implementation utilizing single-beam antennas, each lane willtypically contain an overhead antenna 6 with high gain, circularpolarization, and sufficient bandwidth to cover the entire ISM bandaround 2.45 GHz. The antenna points approximately downward, reducingpotential for cross lane communication. By contrast, antenna pointingangles near horizontal can allow large vehicles to block the direct RFpath of smaller vehicles in the same lane, and multiple phones indifferent lanes to be transacted with at relatively longer distanceswhere the beams have spread significantly. Pointing downward, therefore,allows easier control of the capture zone.

A high gain antenna with low side lobes and a sharp beam roll off willminimize RF leakage into the adjacent lanes. This pattern must beconsistent across the entire ISM band because BLE uses RF frequenciesspanning the band.

Finally, circular polarization is preferred in the Beacon antennabecause of the variable antenna pattern in the phone. Linear vertical orhorizontal polarization could be used, but circular polarization ispreferred so as to make the communication link to the phone lesssensitive to the orientation of the phone in the vehicle. This allowsthe user more flexibility for the phone's location inside the vehicle,including the seat, in pocket, on the vehicle's dash board, or in itscenter console, creating good RF link performance unaffected byorientation of the phone. Most antennas targeting 2.45 GHz devices inmobile phones have nulls in each plane. The location and depth of thenulls is dependent on frequency and polarization, and a circularlypolarized Beacon antenna will provide polarization diversity.

Frequency diversity is a de-facto feature of the system when usingwireless protocols that utilize a sufficiently large RF frequency band.A large operating frequency band causes phone antenna nulls and RF fadesto move as frequency changes. In a BLE system, for example, advertisingchannels hop between 2402, 2426, and 2480 MHz. The antenna operatingband must be at least this large to take advantage of this.

The required antenna features of the system described above enhancechances of the in-lane beacon transacting with the phone, as opposed tothe adjacent-lane beacon. It does not entirely rule out cross lanetransactions, so an appropriate system will monitor the number oftransactions on all beacons for a specific phone and choose the travellane appropriately.

Multi-Beam Antenna

With smart phones acting as transmitters, the receiving antennas locatedin the toll plaza may take multiple forms. One embodiment is a pair ofmulti-beam antennas straddling the roadside to enableangle-of-arrival-based lane determination. A common form for themulti-beam antennas are planar arrays with Butler matrix feed systems.

Butler matrix antenna configurations are known in the art but can beuniquely applied in this case with either the WiFi or the Bluetooth® LEradio signals to track vehicles in which the phones are present andassociated. Other forms of directed antenna configurations are alsoknown, see for example U.S. Pat. No. 5,592,181, which is incorporated byreference herein. For example, see the thesis paper: Implementation of a8×8 Butler Matrix in Microstrip by Henrik Nord incorporated in AppendixA of the provisional Application Ser. 62/214,638 filed Sep. 4, 2015 andthe slide presentation Design and Implementation of ButlerMatrix—Simultaneous Beam Formation, by Harish Rajagopalan, incorporatedas Appendix B in the provisional Application Ser. 62/214,638 filed Sep.4, 2015. Both of these documents are incorporated by reference herein.The multi-beam antennas can be used on their own for both communicationsand tracking, but may also be used with a set of low gain antennas wherethe low gain antennas cover the entire area of interest to allow moretime for reliable communications roadway and the multi-beam antennasused for tracking only or primarily for tracking.

The Butler matrix is a well-known beam-former, producing N beams from Ngroups of radiators. FIG. 5 is a diagram of an 8×8 Butler matrix. It canbe thought of as a hardware realization of a Fourier transform, andindeed the diagram is reminiscent of an FFT.

FIG. 6 shows the results of experimental evaluation conducted with twomulti-beam antennas installed roadside. The test results showedsignificant ability to locate the vehicle position across 6 lanes. Thegraph shows post-processed data: the computed lane number as a functionof time, and the total number of hits for each lane. Multipath isevident in hits for lanes beside lane 3 (the actual travel lane). Onecar at a time was tested.

These experiments were conducted with a 2.45 GHz radio in the vehicleunder the dash on the left side of the vehicle, which is a non-idealposition for the transmitter in the vehicle because the signal mustreach the receiver via multi-path. Similar, but less severe multi-pathcan be expected based on the typical locations users will have theirphone in the vehicle, be it in the user's pocket, belt, purse, cupholder or passenger seat. All of these locations will potentially seemulti-path between the smart phone and exterior antennas, but probablyless severe than the conditions of the experiment. Notwithstanding themore severe multi path conditions for the experiment, reasonably goodposition results were obtained in determining the lane of travel byassigning the transmitter to a lane position by summing the number ofpoints where the peak beam signal strength of the Butler matrix antennasindicated an intersection point in a particular lane and assigning thelane position to the lane with the greatest number of such points as thevehicle traverses a section of roadway.

To use the system, users download an application to the smart phone.Upon download of the phone application, the user will use applicationsupported account management features to set up an account with theappropriate toll authority or third party service provider, create alink between the unique ID/address information to the account, provide ameans for the settlement of toll charges associated with the unique ID(such as a credit card)

The test results (FIG. 6) showed significant ability to locate thevehicle position across 6 lanes. The graph shows post-processed data:the computed lane number as a function of time, and the total number ofhits for each lane. Multipath is evident in hits for lanes beside lane 3(the actual travel lane). One car at a time was tested.

Mileage Reporting System for Mileage Based User Fees

In another embodiment, the smart phone application is configured tosupport the accurate and secure self-reporting of miles driven bytaxpayers in jurisdictions where taxes are collected based on the numberof miles driven in the jurisdiction. As a possible way to meet policyobjectives, California and Oregon have pilot projects and considerationis being given to similar taxation system by the U.S. FederalGovernment. However a practical, private, easy, accurate and secure wayfor user to report the mileage and corresponding tax has been lacking.

The basic reporting approach of the invention involves installing BLEbeacons at locations convenient to the motorist such as gas stations,oil change facilities, smog check stations and car washes, calledreporting facilities. In the preferred embodiment drivers self-reportthe mileage and pay the tax periodically, perhaps once per quarter orper year. The phone application of the invention makes it easy andsecure to report mileage.

The design of the phone application is such that the user enters areporting facility and parks in a designated location designed to becovered by the BLE beacon. The beacon data includes location data and asecure identifier. In one embodiment the secure identifier is anencrypted combination of the time and location information. Thelocations are selected and high gain antennas placed such that no morethan one vehicle can be parked in a designated location simultaneously.

The phone application recognizes the beacon, processes the data, andstarts the procedure. The user is prompted to take a photo of thevehicle odometer reading, and the application records the fact that thephoto was taken proximate to the secure beacon and a specific date andtime. Next the user is prompted to take a picture of the VIN or licenseplate number, and the application records that the VIN is also proximateto the same secure beacon at the same date/time (within a tolerance).This ensures that in fact the odometer photo and the VIN or licenseplate number photo are from the same vehicle.

The phone application applies OCR techniques to the odometer reading tocreate a data element and compares this reading to the previous reading.The application calculates the tax based on the difference in mileagefrom the previous reading.

Once the tax owed is calculated the phone application then prompts theuser to make payment by electronic check, ACH, or credit card, Pay Pal®or other known payment systems. These payment methods can be newlyestablished at the time of payment or stored at the user's preference.The user makes payment and an official receipt is sent to the usersstored e-mail address.

If a user wishes to account for miles driven on non-taxable roads thatmight be exempt from the tax, such as out of state or private roads, aBLE beacon can similarly be placed at the access point to thosefacilities. For example, BLE beacons can be installed at the stateborders to account for out of state miles. The phone application detectsthese border beacons to validate that the vehicle has indeed crossed thestate line. Alternatively two beacons in sequence could be used tovalidate the direction of travel at the state line. The secure borderbeacon location data is stored in the application. The phone applicationthen sets up a large position change feature on the phone, so that thephone application is activated by the phone upon a significant change inposition, or after a certain period of time has elapsed. Uponactivation, the application evaluates the data from at least one GPS fixto determine the estimated miles driven from the border beacon location.Upon each subsequent activation of the application on the phone a newGPS fix is taken and an incremental number of miles driven out of state.This process continues until the phone crosses another border beaconsystem indicating re-entry into the state (or alternatively, a GPSposition fix within the state). The total accumulated miles out ofdriven out of state can be determined.

In addition, if policy dictates the need to collect mileage based tax orfee at different rates on different types of roadways this can beaccommodated by the system design. For example, if a different rate isto be charged for controlled access highways than arterials, beacons canbe placed on the controlled access points to identify entry and exitpoints which allow the determination of total miles driven on controlledaccess highways. Those miles can be accumulated in a separate buffersuch that at the time of tax payment calculation the tax due can bedetermined based upon the differentiated miles driven. Similarly, whenmiles are driven on a toll facility which might typically be exempt froma mileage charge, BLE beacons on the toll facility can be segregated tocalculate the correct adjustment to the tax owed at time of payment. Ofcourse as described in this disclosure the BLE beacons can work with thephone application to be the primary method of toll collection, providinga seamless approach for the user to pay for services rendered.

What is claimed is:
 1. A mobile device, comprising: a receiverconfigured to receive signals transmitted from a stationary signaltransmitting system associated with tracking vehicles, wherein themobile device is located in a first vehicle; and a processor configuredto: determine a signal strength for each of the received signals, anddetermine a position of the first vehicle based on the determined signalstrengths.
 2. The mobile device of claim 1, wherein the received signalscomprise Bluetooth low energy (BLE) or WiFi signals transmitted from thestationary signal transmitting system.
 3. The mobile device of claim 2,wherein the BLE signals or WiFi signals comprise advertisement signalscomprising at least one of: a beacon identifier, an identifierassociated with the stationary signal transmitting system, a laneidentifier, or a time.
 4. The mobile device of claim 1, wherein whendetermining the signal strength for each of the received signals, theprocessor is configured to: determine the signal strength of each of aplurality of BLE or WiFi signals transmitted from at least one antennaassociated with the stationary signal transmitting system, and generatevehicle position information relative to the at least one antenna basedon the determined signal strengths.
 5. The mobile device of claim 1,wherein the stationary signal transmitting system comprises a pluralityof antennas distributed at least one of across or adjacent a roadway ora multi-lane tolling plaza, and wherein the receiver is configured toreceive unique advertisement signals transmitted from at least some ofthe plurality of antennas.
 6. The mobile device of claim 5, wherein theprocessor is further configured to: determine the position of the firstvehicle relative to a lane on the roadway based on signal strengths ofthe received advertisement signals.
 7. The mobile device of claim 6,wherein when determining the position of the first vehicle, theprocessor is configured to determine the position of the first vehiclebased on at least one advertisement signal having a highest signalstrength.
 8. The system of claim 1, wherein the receiver is configuredto receive a plurality of unique advertisements transmitted from aplurality of antennas associated with the stationary signal transmittingsystem.
 9. The mobile device of claim 1, wherein the processor isconfigured to: generate a response to a received BLE beacon signal withunique identification information.
 10. The mobile device of claim 9,further comprising: a BLE transmitter configured to transmit theresponse.
 11. The mobile device of claim 1, wherein when determining asignal strength, the processor is configured to: identify a receivedsignal strength indicator (RSSI) for each of each of the receivedsignals, wherein each of the received signals comprises an identifierassociated with a particular lane.
 12. The mobile device of claim 11,wherein when determining the position of the first vehicle, theprocessor is configured to: determine, over a period of time, a highestRSSI associated with one of the received signals, and identify a laneassociated with the highest RSSI based on the identifier.
 13. The mobiledevice of claim 12, wherein the processor is further configured to:establish an account with a toll authority or third party associatedwith the toll authority, and provide for payment to the toll authorityor third party based on the identified lane.
 14. The mobile device ofclaim 11, wherein when determining the position of the first vehicle,the processor is configured to: determine, over a period of time, anaverage RSSI associated with each of a plurality of received signalsassociated with a particular identifier, and identify a lane associatedwith the highest average RSSI based on the particular identifier.
 15. Anon-transitory computer-readable medium comprising instructions, whichwhen executed by a processor of a mobile device, cause the processor to:receive signals transmitted from a stationary signal transmitting systemassociated with tracking vehicles; determine a signal strength for eachof the received signals; and determine a position of a vehicle in whichthe mobile device is located based on the determined signal strengths.16. The non-transitory computer-readable medium of claim 15, whereinwhen determining the signal strength for each of the received signals,the instructions cause the processor to: determine the signal strengthof each of a plurality of Bluetooth low energy (BLE) or WiFi signalstransmitted from at least one antenna associated with the stationarysignal transmitting system, and generate position information for thevehicle relative to the at least one antenna based on the determinedsignal strengths.
 17. The non-transitory computer-readable medium ofclaim 15, wherein when determining the position of the vehicle, theinstructions cause the processor to: determine the position of thevehicle relative to a lane on the roadway based on signal strengths ofthe received signals.
 18. The non-transitory computer-readable medium ofclaim 15, wherein when determining the signal strength for each of thereceived signals, the instructions cause the processor to: identify areceived signal strength indicator (RSSI) for each of each of thereceived signals, wherein each of the received signals comprises anidentifier associated with a particular lane.
 19. The non-transitorycomputer-readable medium of claim 18, wherein when determining theposition of the vehicle, the instructions cause the processor to:determine, over a period of time, a highest RSSI associated with one ofthe received signals, and identify a lane associated with the highestRSSI based on the identifier.
 20. The non-transitory computer-readablemedium of claim 19, wherein the instructions further cause the processorto: establish an account with a toll authority or third party associatedwith the toll authority, and provide for payment to the toll authorityor third party based on the identified lane.